The Merriam-Webster Dictionary site is an epicurean and sometimes mercurial presentation of language that tantalizes even the most Draconian and martinet-ish of word lovers.
A case in point: The delightful “Eponym Quiz,” which tests your knowledge of many of the words in the previous sentence that are based on the names of people. You’ll have to take the quiz to discover who gave their names to those words, because we don’t want to give you an unfair advantage. We’ll offer others instead.
In traditional usage an “eponym” is something that has loaned its name to something else. By extension, in everyday usage and many dictionaries, the “eponym” is also the thing that borrowed the name.
Some eponyms have retained the capitalization of their namesakes, such as “Bakelite” (1909), a trademark for the first synthetic plastic, created by Leo Baekeland. Most have lost their capitalization, though some are recognizable as deriving from names. For example, “béchamel” sauce, named for the Marquis Louis de Béchamel, a steward to Louis XIV of France in the late 17th century. The sauce had probably been brought to France at least a hundred years earlier, but the Marquis got naming rights. (The Oxford English Dictionary says it first appeared in English in 1789 spelled “bishemel.”)
If you drive a truck, thank Rudolf Diesel. Raised mostly in France and England, Diesel later moved to Germany, where in 1892 he obtained the first patent for the technology that later became the “diesel” engine.
Owners of fish tanks might have schools of a tiny fish called a “guppy.” R.J. Lechmere Guppy was a British engineer with an interest in flora and fauna who worked on the island of Trinidad. In 1866, he sent a sample of a small Trinidadian fish to the British Museum, which named it Girardinus guppii in his honor. As in the case of béchamel sauce, however, he was not the original source: that same fish had been described years earlier by a naturalist in Venezuela. The fish was later formally renamed Lebistes reticulatus, but kept its nickname.
Smokers, chawers, and vapers can thank (or blame) Jean Nicot. In the late 16th century, he was the French ambassador to Portugal, where a botanist friend explained the healing powers of a tobacco plant. He sent news of this wonder to France, and supposedly sent tobacco snuff to the queen, Catherine de Medici, to treat her headaches. “Nicotiana” was the name of the plant; “nicotine,” the substance derived from it, did not appear in English until 1817, the OED says. (Of course, this ignores the fact that tobacco had been in use in the Americas long before the Europeans had even heard of it.)
Last, one elegant artform owes its name to a skinflint. Étienne de Silhouette was a finance minister under Louis XV, who was known for trying to squeeze as much out of taxpayers and budgets as he could. As Merriam-Webster says, he liked to make cut-paper shadow portraits. “The phrase à la Silhouette came to mean ‘on the cheap,’ and portraits like the ones he produced were (satirically) bestowed with his name as well.” He has been shadowed by his “eponym” since 1798.